1. Field of the Invention:
This invention pertains to blowing or foaming agents. More specifically, this invention relates to blowing agents for isocyanate-based foams. Even more particularly, the present invention concerns blowing agents to be used as replacements for chlorofluorocarbon blowing agents.
2. Brief Discussion of the Prior Art:
In the past trichloromonofluoromethane-based blowing agents (CFC's) such as CFC-11 (CCl.sub.3 F) have been the most desirable blowing agents for isocyanate-based foams, such as rigid and flexible urethane and isocyanurate foams because of its many advantages, such as, low thermal conductivity, non-reactivity, low boiling point, non-flammability, and its non-collapse effect in foam preparation.
In recent years however, it is becoming increasingly obvious that the use of chlorofluorocarbons is depleting the ozone layer in the stratosphere and resulting in serious environmental problems on earth. The use and production of various chlorofluorocarbons is being restricted and thus alternatives are necessary. Alternatives for the chlorofluorocarbon blowing agents have been found in the hydrogen-containing chlorofluorocarbon (HCFC), such as HCFC-123 (CHCl.sub.2 CF.sub.3) and hydrocarbon blowing agents.
The HCFC's have relatively short life times in the atmosphere and decompose before they reach the stratosphere. These HCFC compounds, however, present the disadvantages of higher cost and relatively higher thermal conductivity of a foam in which they are used.
Hydrocarbons are flammable and result in flammable foams.
It is therefore desirable to find a new blowing agent as an alternative to HCFC's as well as the CFC's